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  • CLASSES

    Alpha Adrenoreceptor Antagonists/Alpha Blockers
    Alpha-Blockers

    DEA CLASS

    Rx

    DESCRIPTION

    Alpha-adrenergic blocker; used for HTN and BPH; duration of action longer than prazosin but is shorter than doxazosin; greater efficacy for BPH when compared to finasteride.

    COMMON BRAND NAMES

    Hytrin

    HOW SUPPLIED

    Hytrin/Terazosin/Terazosin Hydrochloride Oral Cap: 1mg, 2mg, 5mg, 10mg

    DOSAGE & INDICATIONS

    For the treatment of hypertension.
    NOTE: A landmark clinical trial (ALLHAT), published in 2000, compared another alpha-blocker, doxazosin, to chlorthalidone in the treatment of high-risk hypertensive patients. In this study, only the diuretic significantly reduced the risk of combined cardiovascular disease events, especially heart failure. These results led to discontinuation of the alpha-blocker treatment arm of the study.
    Oral dosage
    Adults

    Initially, 1 mg PO once daily at bedtime. Increase gradually if necessary. Average maintenance dose is 1—5 mg once daily. Maximum dosage is 20 mg/day, given in divided doses every 12 hours. At this higher dosage, the daily dose can be divided and administered at 12-hour intervals. When adding additional hypotensive agents or diuretics to terazosin therapy, decrease the dosage of terazosin and then gradually increase as needed.

    Geriatric

    See adult dosage. Elderly patients may be more sensitive to the hypotensive and adverse effects (dry mouth and drowsiness) of terazosin. Adjust dosage based on clinical response.

    For the treatment of symptomatic benign prostatic hyperplasia (BPH).
    Oral dosage
    Adults

    Initially, 1 mg PO once daily at bedtime. Doses are increased to 2 mg, 5 mg, then 10 mg once daily based on improvement of symptoms and urine flow rates. Maintenance doses of 5—10 mg/day have been used. Maximum dosage is 20 mg/day, given in divided doses every 12 hours. In a head-to-head comparison with finasteride, terazosin was initiated at a dose of 1 mg PO once daily at bedtime and gradually increased to 10 mg PO once daily at bedtime. The dose could be adjusted downward if adverse effects appeared. At the end of the study, 80% of the men were receiving the full dose.

    Geriatric

    See adult dosage. Elderly patients may be more sensitive to the hypotensive and adverse effects (dry mouth and drowsiness) of terazosin. Adjust dosage based on clinical response.

    MAXIMUM DOSAGE

    Adults

    20 mg/day PO.

    Elderly

    20 mg/day PO.

    Adolescents

    Safety and efficacy have not been established.

    Children

    Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    No specific recommendations are available for hepatic disease. Since terazosin is extensively metabolized, it is prudent to start with the lowest initial adult dosage (1 mg PO once daily at bedtime). Monitor and adjust dosage based on clinical response.

    Renal Impairment

    No dosage adjustment is needed.
     
    Intermittent hemodialysis
    No dosage adjustment is needed. Terazosin is highly protein bound and only 10% is removed during hemodialysis, and supplemental doses are not needed.

    ADMINISTRATION

     
    NOTE: If terazosin therapy is interrupted for several days, restart therapy with initial dosing regimen.

    Oral Administration

    Terazosin may be administered without regard to meals. Food may delay the time to peak concentrations, but has no significant effect on terazosin bioavailability.
     
    In patients with feeding tubes:
    NOTE: Terazosin binds to the soft-gelatin capsule in which it is formulated making it difficult to completely extract the contents when the liquid is squeezed from the capsule. The following strategy has been recommended as an alternative method of oral administration in patients with feeding tubes:
    Place the capsule in a cup containing 60 ml of warm tap water (100—110 degrees F). Stir until the liquid in the capsule spills from the ruptured shell (about 5 minutes). Continue stirring until the capsule dissolves and the solution is homogeneous (5—10 minutes). The solution color depends on the color of the capsule. Draw the solution into an oral syringe and administer through the feeding tube. Flush the tube with water following administration.

    STORAGE

    Hytrin:
    - Protect from light
    - Protect from moisture
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F

    CONTRAINDICATIONS / PRECAUTIONS

    Angina, orthostatic hypotension, syncope

    Terazosin can cause orthostatic hypotension and syncope, which can be hazardous for patients in occupations that require alertness. This effect can be dramatic after the initial dose. The addition of terazosin to other antihypertensive agents can cause a rapid decrease in blood pressure (see Drug Interactions). Terazosin therapy should be initiated cautiously in patients receiving other antihypertensive agents. Terazosin should be used with caution in patients with angina pectoris because severe hypotension may cause or worsen angina.

    Geriatric

    Geriatric patients may be more sensitive to the hypotensive and adverse effects (dry mouth and drowsiness) of terazosin. Monitor older adult patients closely. According to the Beers Criteria, terazosin is considered a potentially inappropriate medication (PIM) for use in geriatric patients and should be avoided as routine treatment of hypertension in this population due to the high risk of orthostatic hypotension and the availability of alternative agents with a superior benefit to risk profile. In addition, the Beers expert panel recommends avoiding terazosin in geriatric patients with syncope due to an increased risk of orthostatic hypotension or bradycardia, and also avoiding terazosin in elderly females with urinary incontinence, regardless of cause or type, because aggravation of incontinence may occur. The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities (LTCFs). According to the OBRA guidelines, antihypertensive regimens should be individualized to achieve the desired outcome while minimizing adverse effects. Antihypertensives may cause dizziness, postural hypotension, fatigue, and there is an increased risk for falls. Terazosin can cause significant hypotension and syncope during the first few doses; therefore, the dose should be administered at bedtime initially, and the drug slowly titrated as needed. There are many drug interactions that can potentiate the effects of antihypertensives. Some agents require a gradual taper to avoid adverse consequences caused by abrupt discontinuation. In addition, when terazosin is infrequently used as a treatment for urinary incontinence, assessment of the underlying causes and identification of the type/category of urinary incontinence needs to be documented prior to or soon after the time of initiating treatment. These medications have specific and limited indications based on the cause and categorization of incontinence. Patients should be assessed periodically for medication effects on urinary incontinence as well as lower urinary tract symptoms and treatment tolerability.

    Pregnancy

    No adequate, well-controlled studies in pregnant women have been done to assess the safety of terazosin during pregnancy. Terazosin should be used during pregnancy only if the benefits to the mother outweigh the risks to the fetus. Terazosin is classified as FDA pregnancy category C.

    Breast-feeding

    Caution is advisable for breast-feeding mothers because it is not known whether terazosin distributes into breast milk. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    Ocular surgery

    Patients receiving or who have previously received treatment with alpha-1 blockers, like terazosin, may be at risk for intraoperative floppy iris syndrome during surgery for cataracts (ocular surgery). Intraoperative floppy iris syndrome is a small pupil syndrome variant that is characterized by a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs, and potential prolapse of the iris toward the phacoemulsification incisions. There does not appear to be a benefit of stopping alpha-1 blocker therapy prior to cataract surgery, but ophthalmologists should be prepared for possible modifications to their surgical technique such as the use of iris hooks, iris dilator rings, or viscoelastic substances.

    Priapism

    Rarely, terazosin, like other alpha adrenergic antagonists, has been associated with priapism (persistent painful penile erection unrelated to sexual activity). Priapism, if not treated promptly, can result in irreversible damage to the erectile tissue. Patients who have an erection lasting greater than 4 hours, whether painful or not, should seek emergency medical attention.

    ADVERSE REACTIONS

    Severe

    atrial fibrillation / Early / Incidence not known
    visual impairment / Early / Incidence not known
    anaphylactoid reactions / Rapid / Incidence not known

    Moderate

    peripheral edema / Delayed / 0.9-5.5
    palpitations / Early / 4.3-4.3
    orthostatic hypotension / Delayed / 1.3-3.9
    dyspnea / Early / 1.7-3.1
    sinus tachycardia / Rapid / 1.9-1.9
    impotence (erectile dysfunction) / Delayed / 1.6-1.6
    blurred vision / Early / 1.3-1.6
    amblyopia / Delayed / 1.3-1.3
    edema / Delayed / 0.9-0.9
    depression / Delayed / 0.3-0.3
    chest pain (unspecified) / Early / Incidence not known
    peripheral vasodilation / Rapid / Incidence not known
    constipation / Delayed / Incidence not known
    priapism / Early / Incidence not known
    urinary incontinence / Early / Incidence not known
    floppy iris syndrome / Delayed / Incidence not known
    conjunctivitis / Delayed / Incidence not known
    gout / Delayed / Incidence not known
    thrombocytopenia / Delayed / Incidence not known

    Mild

    dizziness / Early / 9.1-19.3
    headache / Early / 16.2-16.2
    asthenia / Delayed / 7.4-11.3
    nasal congestion / Early / 1.9-5.9
    drowsiness / Early / 3.6-5.4
    nausea / Early / 1.7-4.4
    paresthesias / Delayed / 2.9-2.9
    sinusitis / Delayed / 2.6-2.6
    influenza / Delayed / 2.4-2.4
    back pain / Delayed / 2.4-2.4
    anxiety / Delayed / 2.3-2.3
    rhinitis / Early / 1.9-1.9
    vertigo / Early / 1.4-1.4
    syncope / Early / 0.6-0.6
    libido decrease / Delayed / 0.6-0.6
    weight gain / Delayed / 0.5-0.5
    arthralgia / Delayed / 1.0
    myalgia / Early / 1.0
    arthropathy / Delayed / 1.0
    insomnia / Early / Incidence not known
    vomiting / Early / Incidence not known
    xerostomia / Early / Incidence not known
    diarrhea / Early / Incidence not known
    flatulence / Early / Incidence not known
    abdominal pain / Early / Incidence not known
    dyspepsia / Early / Incidence not known
    increased urinary frequency / Early / Incidence not known
    infection / Delayed / Incidence not known
    epistaxis / Delayed / Incidence not known
    cough / Delayed / Incidence not known
    pharyngitis / Delayed / Incidence not known
    tinnitus / Delayed / Incidence not known
    fever / Early / Incidence not known
    pruritus / Rapid / Incidence not known
    rash / Early / Incidence not known
    hyperhidrosis / Delayed / Incidence not known

    DRUG INTERACTIONS

    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Acetaminophen; Chlorpheniramine; Phenylephrine; Phenyltoloxamine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Acetaminophen; Dextromethorphan; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Acetaminophen; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Acetaminophen; Dichloralphenazone; Isometheptene: (Major) Sympathomimetics can antagonize the antihypertensive effects of adrenergic agonists when administered concomitantly. Patients should be monitored for loss of blood pressure control.
    Acetaminophen; Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Acetaminophen; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Acrivastine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Aldesleukin, IL-2: (Moderate) Terazosin may potentiate the hypotension seen with aldesleukin, IL-2.
    Alemtuzumab: (Moderate) Alemtuzumab may cause hypotension. Careful monitoring of blood pressure and hypotensive symptoms is recommended especially in patients with ischemic heart disease and in patients on antihypertensive agents.
    Alfuzosin: (Severe) The pharmacokinetic and pharmacodynamic interactions between alfuzosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects, therefore, alfuzosin should not be administered in combination with other alpha-blockers.
    Alprostadil: (Minor) The concomitant use of systemic alprostadil injection and antihypertensive agents, such as terazosin, may cause additive hypotension. Caution is advised with this combination. Systemic drug interactions with the urethral suppository (MUSE) or alprostadil intracavernous injection are unlikely in most patients because low or undetectable amounts of the drug are found in the peripheral venous circulation following administration. In those men with significant corpora cavernosa venous leakage, hypotension might be more likely. Use caution with in-clinic dosing for erectile dysfunction (ED) and monitor for the effects on blood pressure. In addition, the presence of medications in the circulation that attenuate erectile function may influence the response to alprostadil. However, in clinical trials with alprostadil intracavernous injection, anti-hypertensive agents had no apparent effect on the safety and efficacy of alprostadil.
    Amifostine: (Major) Patients receiving alpha-blockers should be closely monitored during amifostine infusions due to additive effects. Patients receiving amifostine at doses recommended for chemotherapy should have antihypertensive therapy interrupted 24 hours preceding administration of amifostine. If the antihypertensive cannot be stopped, patients should not receive amifostine.
    Amobarbital: (Moderate) Concurrent use of amobarbital with antihypertensive agents may lead to hypotension. Monitor for decreases in blood pressure during times of coadministration.
    Amphetamines: (Major) Amphetamines increase both systolic and diastolic blood pressure and may counteract the activity of some antihypertensive agents. Due to the risk of unopposed alpha-adrenergic activity, amphetamines should be used cautiously with beta-blockers. Increased blood pressure, bradycardia, or heart block may occur due to excessive alpha-adrenergic receptor stimulation. In particular, amphetamines can inhibit the antihypertensive response to guanadrel, an adrenergic antagonist that causes depletion of norepinephrine in the synapse. Close monitoring of blood pressure or the selection of alternative therapeutic agents may be needed.
    Amyl Nitrite: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Apraclonidine: (Minor) Alpha blockers as a class may reduce heart rate and blood pressure. While no specific drug interactions have been identified with systemic agents and apraclonidine during clinical trials, it is theoretically possible that additive blood pressure reductions could occur when apraclonidine is combined with the use of antihypertensive agents. Patients using cardiovascular drugs concomitantly with apraclonidine should have their pulse and blood pressure monitored periodically.
    Aripiprazole: (Minor) Aripiprazole may enhance the hypotensive effects of antihypertensive agents.
    Articaine; Epinephrine: (Major) Sympathomimetics, such as epinephrine, can antagonize the effects of alpha-blockers when administered concomitantly. Patients receiving alpha-blockers can exhibit a decreased pressor response to epinephrine, resulting in an increased risk of developing hypotension and tachycardia. Blood pressure should be monitored closely.
    Asenapine: (Moderate) Secondary to alpha-blockade, asenapine can produce vasodilation that may result in additive effects during concurrent use of antihypertensive agents. The potential reduction in blood pressure can precipitate orthostatic hypotension and associated dizziness, tachycardia, and syncope. If concurrent use of asenapine and antihypertensive agents is necessary, patients should be counseled on measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning and rising slowly from a seated position. Close monitoring of blood pressure is recommended until the full effects of the combination therapy are known.
    Avanafil: (Major) Concurrent use of avanafil and alpha-blockers may lead to symptomatic hypotension in some patients. Avanafil, a phosphodiesterase (PDE5) inhibitor, and alpha-blockers are systemic vasodilators which can lower blood pressure. If vasodilators are used in combination, an additive effect on blood pressure is anticipated. Patients should be stable on alpha-blocker therapy before starting PDE5 inhibitor therapy. If hemodynamic instability is evident on alpha-blocker therapy alone, there is an increased risk of symptomatic hypotension with concomitant PDE5 inhibitor therapy. For patients who are stable on alpha-blocker therapy, PDE5 inhibitors should be started at the 50 mg dose. If a patient is currently receiving an optimized dose of a PDE5 inhibitor, alpha-blocker therapy should be initiated at the lowest dose. Stepwise increases in the alpha-blocker dose may be associated with further hypotension when taking a PDE5 inhibitor. Other variables, such as intravascular volume depletion and other antihypertensive drugs, may affect the safety of concomitant use of PDE5 inhibitors and alpha-blockers.
    Baclofen: (Moderate) Baclofen has been associated with hypotension. Concurrent use with baclofen and antihypertensive agents may result in additive hypotension. Dosage adjustments of the antihypertensive medication may be required.
    Beta-blockers: (Moderate) Orthostatic hypotension may be more likely if beta-blockers are coadministered with alpha-blockers.
    Bortezomib: (Moderate) Patients on antihypertensive agents receiving bortezomib treatment may require close monitoring of their blood pressure and dosage adjustment of their medication. During clinical trials of bortezomib, hypotension was reported in roughly 12 percent of patients.
    Bosentan: (Moderate) Although no specific interactions have been documented, bosentan has vasodilatory effects and may contribute additive hypotensive effects when given with antihypertensive alpha-blockers (i.e., doxazosin, phenoxybenzamine, phentolamine, prazosin, terazosin, and tolazoline).
    Brexpiprazole: (Moderate) Due to brexpiprazole's antagonism at alpha 1-adrenergic receptors, the drug may enhance the hypotensive effects of alpha-blockers and other antihypertensive agents.
    Brompheniramine; Carbetapentane; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Brompheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Cabergoline: (Minor) Cabergoline has minimal affinity for adrenergic receptors; however, it has been associated with hypotension in some instances. Cabergoline should be used cautiously in those receiving antihypertensive agents or other medications known to cause hypotension.
    Carbetapentane; Chlorpheniramine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbetapentane; Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbetapentane; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbetapentane; Phenylephrine; Pyrilamine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbetapentane; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Carbinoxamine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Carbinoxamine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Carbinoxamine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Cariprazine: (Moderate) Orthostatic vital signs should be monitored in patients who are at risk for hypotension, such as those receiving cariprazine in combination with antihypertensive agents. Atypical antipsychotics may cause orthostatic hypotension and syncope, most commonly during treatment initiation and dosage increases. Patients should be informed about measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning, or rising slowly from a seated position. Consider a cariprazine dose reduction if hypotension occurs.
    Cetirizine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Chlophedianol; Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Chlorpheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Cod Liver Oil: (Moderate) Fish oil supplements may cause mild, dose-dependent reductions in systolic or diastolic blood pressure in untreated hypertensive patients. Relatively high doses of fish oil are required to produce any blood pressure lowering effect. Additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents.
    Codeine; Phenylephrine; Promethazine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Co-Enzyme Q10, Ubiquinone: (Moderate) Co-enzyme Q10, ubiquinone (CoQ10) may lower blood pressure. CoQ10 use in combination with antihypertensive agents may lead to additional reductions in blood pressure in some individuals. Patients who choose to take CoQ10 concurrently with antihypertensive medications should receive periodic blood pressure monitoring. Patients should be advised to inform their prescriber of their use of CoQ10.
    Conivaptan: (Moderate) There is potential for additive hypotensive effects when conivaptan is coadministered with antihypertensive agents.
    Desloratadine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Dexchlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Dexmethylphenidate: (Moderate) Dexmethylphenidate can reduce the hypotensive effect of antihypertensive agents, including alpha-blockers. Periodic evaluation of blood pressure is advisable during concurrent use of dexmethylphenidate and antihypertensive agents, particularly during initial coadministration and after dosage increases of dexmethylphenidate.
    Dextromethorphan; Diphenhydramine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Dextromethorphan; Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Dextromethorphan; Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Dextromethorphan; Quinidine: (Moderate) Quinidine can decrease blood pressure and should be used cautiously in patients receiving antihypertensive agents due to the potential for additive hypotension.
    Diazoxide: (Moderate) Additive hypotensive effects can occur with the concomitant administration of diazoxide with other antihypertensive agents. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly. The manufacturer advises that IV diazoxide should not be administered to patients within 6 hours of receiving other antihypertensive agents.
    Diethylpropion: (Major) Diethylpropion has vasopressor effects and may limit the benefit of alpha-blockers. Although leading drug interaction texts differ in the potential for an interaction between diethylpropion and this group of antihypertensive agents, these effects are likely to be clinically significant and have been described in hypertensive patients on these medications.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Diphenhydramine; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Dobutamine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Dopamine: (Major) In general, alpha-blockers should not be used during dopamine infusion. The undesired peripheral vasoconstriction observed with high-dose dopamine is opposed by alpha-adrenergic blockers. The renal, mesenteric, or cerebral vasodilatory properties resulting from dopaminergic-receptor stimulation are not affected by alpha-blockers .
    Drospirenone; Ethinyl Estradiol: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Drospirenone; Ethinyl Estradiol; Levomefolate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Duloxetine: (Moderate) Orthostatic hypotension and syncope have been reported during duloxetine administration. The concurrent administration of antihypertensive agents and duloxetine may increase the risk of hypotension. Monitor blood pressure if the combination is necessary.
    Dutasteride; Tamsulosin: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
    Enflurane: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Ephedrine: (Major) The cardiovascular effects of sympathomimetics, such as ephedrine, may reduce the antihypertensive effects produced by alpha-blockers. Blood pressure and heart rates should be monitored closely to confirm that the desired antihypertensive effect is achieved.
    Epinephrine: (Major) Sympathomimetics, such as epinephrine, can antagonize the effects of alpha-blockers when administered concomitantly. Patients receiving alpha-blockers can exhibit a decreased pressor response to epinephrine, resulting in an increased risk of developing hypotension and tachycardia. Blood pressure should be monitored closely.
    Epoprostenol: (Minor) Epoprostenol can have additive effects when administered with other antihypertensive agents, including alpha-blockers. These effects can be used to therapeutic advantage, but dosage adjustments may be necessary.
    Estradiol Cypionate; Medroxyprogesterone: (Minor) Estrogens can induce fluid retention and may increase blood pressure in some patients; patients who are receiving antihypertensive agents concurrently with hormonal contraceptives should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Estradiol: (Minor) Estrogens can induce fluid retention and may increase blood pressure in some patients; patients who are receiving antihypertensive agents concurrently with hormonal contraceptives should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethanol: (Moderate) Some experts and manufacturers advise that the patient to limit alcohol use while using alpha-blockers. Alcohol-containing beverages may increase the effects of alpha-blockers, which may lower the blood pressure.
    Ethinyl Estradiol: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Desogestrel: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Ethynodiol Diacetate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Etonogestrel: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Levonorgestrel: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Levonorgestrel; Ferrous bisglycinate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Levonorgestrel; Folic Acid; Levomefolate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norelgestromin: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norethindrone Acetate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norethindrone Acetate; Ferrous fumarate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norethindrone: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norethindrone; Ferrous fumarate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norgestimate: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Ethinyl Estradiol; Norgestrel: (Minor) Estrogen-containing oral contraceptive may induce fluid retention and may increase blood pressure in some patients taking antihypertensive agents. Such patients should be monitored to confirm that the desired antihypertensive effect is being obtained.
    Etomidate: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Fexofenadine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Finasteride: (Minor) Terazosin has been reported to increase peak concentrations of finasteride by 16% and AUC by 31% when the two agents are coadministered. The interaction is of minor importance.
    Fish Oil, Omega-3 Fatty Acids (Dietary Supplements): (Moderate) Co-enzyme Q10, ubiquinone (CoQ10) may lower blood pressure. CoQ10 use in combination with antihypertensive agents may lead to additional reductions in blood pressure in some individuals. Patients who choose to take CoQ10 concurrently with antihypertensive medications should receive periodic blood pressure monitoring. Patients should be advised to inform their prescriber of their use of CoQ10.
    Fluoxetine; Olanzapine: (Moderate) Olanzapine may induce orthostatic hypotension and thus enhance the effects of antihypertensive agents.
    Fospropofol: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    General anesthetics: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Guaifenesin; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Haloperidol: (Moderate) In general, haloperidol should be used cautiously with antihypertensive agents due to the possibility of additive hypotension.
    Halothane: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Hawthorn, Crataegus laevigata: (Moderate) Hawthorn, Crataegus laevigata may lower peripheral vascular resistance. Hawthorn use in combination with antihypertensive agents may lead to additional reductions in blood pressure in some individuals. Patients receiving hawthorn concurrently with antihypertensive medications should receive periodic blood pressure monitoring.
    Hydralazine; Isosorbide Dinitrate, ISDN: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Hydrocodone; Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Hydrocodone; Potassium Guaiacolsulfonate; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Hydrocodone; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Ibuprofen; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Iloperidone: (Moderate) Secondary to alpha-blockade, iloperidone can produce vasodilation that may result in additive effects during concurrent use with antihypertensive agents. The potential reduction in blood pressure can precipitate orthostatic hypotension and associated dizziness, tachycardia, and syncope. If concurrent use of iloperidone and antihypertensive agents is necessary, patients should be counseled on measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning and rising slowly from a seated position. Close monitoring of blood pressure is recommended until the full effects of the combination therapy are known.
    Iloprost: (Moderate) The effects of iloprost on blood pressure may be additive to those of antihypertensive agents. Lower doses of the antihypertensive may be needed with combined treatment.
    Isocarboxazid: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives. Careful monitoring of blood pressure is suggested during concurrent therapy with antihypertensives such as alpha-blockers. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider.
    Isoflurane: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Isoproterenol: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Isosorbide Dinitrate, ISDN: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Isosorbide Mononitrate: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Ketamine: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Levomilnacipran: (Moderate) Levomilnacipran has been associated with an increase in blood pressure. The effectiveness of antihypertensive agents, including alpha-blockers, may be diminished during concurrent use of levomilnacipran. It is advisable to monitor blood pressure if the combination is necessary.
    Lofexidine: (Major) Because the central alpha-2 agonist effects of lofexidine can cause hypotension and orthostasis, the drug should be avoided, if possible, in combination with other medications that can significantly decrease blood pressure such as the antihypertensive alpha-blockers. If coadministration is required, blood pressure should be monitored, particularly after dose changes of either agent. Adjustments should be made as clinically indicated. Patients being given lofexidine in an outpatient setting should be capable of and instructed on self-monitoring for hypotension, orthostasis, bradycardia, and associated symptoms. If clinically significant or symptomatic hypotension and/or bradycardia occur, the next dose of lofexidine should be reduced in amount, delayed, or skipped.
    Loratadine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Lovastatin; Niacin: (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. This effect is of particular concern in the setting of acute myocardial infarction, unstable angina, or other acute hemodynamic compromise.
    Lurasidone: (Moderate) Due to the antagonism of lurasidone at alpha-1 adrenergic receptors, the drug may enhance the hypotensive effects of alpha-blockers and other antihypertensive agents. If concurrent use of lurasidone and antihypertensive agents is necessary, patients should be counseled on measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning and rising slowly from a seated position. Close monitoring of blood pressure is recommended until the full effects of the combination therapy are known.
    Mestranol; Norethindrone: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients; monitor patients receiving concurrent therapy to confirm that the desired antihypertensive effect is being obtained.
    Methohexital: (Moderate) Concurrent use of methohexital and alpha-blockers increases the risk of developing hypotension and hypothermia.
    Methylphenidate: (Moderate) Methylphenidate can reduce the hypotensive effect of antihypertensive agents such as alpha-blockers. Periodic evaluation of blood pressure is advisable during concurrent use of methylphenidate and antihypertensive agents, particularly during initial coadministration and after dosage increases of methylphenidate.
    Midodrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Milnacipran: (Moderate) Milnacipran has been associated with an increase in blood pressure. The effectiveness of antihypertensive agents may be diminished during concurrent use of milnacipran. It is advisable to monitor blood pressure if the combination is necessary.
    Milrinone: (Moderate) Concurrent administration of antihypertensive agents could lead to additive hypotension when administered with milrinone. Titrate milrinone dosage according to hemodynamic response.
    Naproxen; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Nesiritide, BNP: (Major) The potential for hypotension may be increased when coadministering nesiritide with antihypertensive agents.
    Niacin, Niacinamide: (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. This effect is of particular concern in the setting of acute myocardial infarction, unstable angina, or other acute hemodynamic compromise.
    Niacin; Simvastatin: (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. This effect is of particular concern in the setting of acute myocardial infarction, unstable angina, or other acute hemodynamic compromise.
    Nicotine: (Moderate) Nicotine use may reduce the clinical effects of the alpha-blockers. If significant changes in nicotine intake occur, the dosages of these drugs may need adjustment.
    Nitrates: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Nitroglycerin: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary.
    Nitroprusside: (Moderate) Additive hypotensive effects may occur when nitroprusside is used concomitantly with other antihypertensive agents. Dosages should be adjusted carefully, according to blood pressure.
    Nonsteroidal antiinflammatory drugs: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Norepinephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly. Also, because norepinephrine is an alpha-adrenergic agonist, drugs with alpha-blocking activity such as alpha-blockers directly counteract the vasopressor effects of norepinephrine.
    Olanzapine: (Moderate) Olanzapine may induce orthostatic hypotension and thus enhance the effects of antihypertensive agents.
    Oxymetazoline: (Major) Caution is advised when administering terazosin with oxymetazoline. Terazosin, an alpha adrenergic blocker, would likely antagonize the sympathomimetic effects of oxymetazoline, alpha adrenergic agonists; thereby reducing the effectiveness of oxymetazoline.
    Paliperidone: (Moderate) Paliperidone may cause orthostatic hypotension, thereby enhancing the hypotensive effects of antihypertensive agents. Orthostatic vital signs should be monitored in patients receiving terazosin who are susceptible to hypotension.
    Pentoxifylline: (Moderate) Pentoxifylline has been used concurrently with antihypertensive drugs (beta blockers, diuretics) without observed problems. Small decreases in blood pressure have been observed in some patients treated with pentoxifylline; periodic systemic blood pressure monitoring is recommended for patients receiving concomitant antihypertensives. If indicated, dosage of the antihypertensive agents should be reduced.
    Phendimetrazine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Phenelzine: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives. Careful monitoring of blood pressure is suggested during concurrent therapy with antihypertensives such as alpha-blockers. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider.
    Phentermine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Phentermine; Topiramate: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Phenylephrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Phenylephrine; Promethazine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Prilocaine; Epinephrine: (Major) Sympathomimetics, such as epinephrine, can antagonize the effects of alpha-blockers when administered concomitantly. Patients receiving alpha-blockers can exhibit a decreased pressor response to epinephrine, resulting in an increased risk of developing hypotension and tachycardia. Blood pressure should be monitored closely.
    Procainamide: (Moderate) Procainamide can decrease blood pressure and should be used cautiously in patients receiving antihypertensive agents. Intravenous administration of procainamide is more likely to cause hypotensive effects.
    Procaine: (Moderate) Local anesthetics may cause additive hypotension in combination with antihypertensive agents.
    Propofol: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by alpha-blockers. Monitor blood pressure and heart rate.
    Quinidine: (Moderate) Quinidine can decrease blood pressure and should be used cautiously in patients receiving antihypertensive agents due to the potential for additive hypotension.
    Rasagiline: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives. Careful monitoring of blood pressure is suggested during concurrent therapy with antihypertensives such as alpha-blockers. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider.
    Risperidone: (Moderate) Risperidone may induce orthostatic hypotension and thus enhance the hypotensive effects of antihypertensive agents. Lower initial doses or slower dose titration of risperidone may be necessary in patients receiving antihypertensive agents concomitantly.
    Ritodrine: (Major) Sympathomimetics can antagonize the effects of antihypertensives such as alpha-blockers when administered concomitantly.
    Selegiline: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives. Careful monitoring of blood pressure is suggested during concurrent therapy with antihypertensives such as alpha-blockers. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider.
    Sevoflurane: (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Sildenafil: (Moderate) Patients should be stable on alpha-blocker therapy before initiating therapy with sildenafil or other phosphodiesterase type 5 (PDE5) inhibitors; the lowest dose should be used to initiate therapy. Conversely, patients already receiving an optimized dose of a PDE5 inhibitor should be started on the lowest dose of an alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Using sildenafil and alpha-blockers together may reduce blood pressure significantly in some patients and may lead to symptomatic hypotension. PDE5 inhibitors and alpha blockers are both vasodilators with blood pressure lowering effects. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers.The manufacturer reports on 3 studies assessing the interaction between sildenafil with doxazosin. In these studies, healthy patients with BPH were stabilized on doxazosin for at least 14 days before receiving sildenafil or placebo. Patients receiving the combination of sildenafil and doxazosin had greater decreases in blood pressure than those receiving doxazosin and placebo. No episodes of syncope were reported in these studies. In one published study, sildenafil and doxazosin were used together in patients with non-organic erectile dysfunction refractory to sildenafil monotherapy; blood pressure was not significantly altered in this study. The safety of using PDE5 inhibitors and alpha-blockers together may also be affected by other factors, such as intravascular volume depletion and coadministration of other antihypertensive medications.
    Silodosin: (Major) The pharmacodynamic effects of coadministration of silodosin and other alpha-blockers has not been studied. Additive effects on blood pressure or an increased incidence of adverse reactions common to alpha-blocker treatment is possible. Therefore, combined use of silodosin and other alpha-blockers is not recommended.
    Tadalafil: (Major) Concurrent use of tadalafil and alpha-blockers may lead to symptomatic hypotension in some patients. The manufacturer of tadalafil states that patients should be stabilized on alpha blocker therapy prior to starting tadalafil at the lowest recommended dose. If hemodynamic instability is evident on alpha-blocker therapy alone, there is an increased risk of symptomatic hypotension with concomitant tadalafil therapy. Likewise, for patients currently receiving an optimized dose of tadalafil, alpha-blocker therapy should be initiated at the lowest dose. Stepwise increases in the alpha blocker dose may be associated with further hypotension when taking tadalafil. Other variables, such as intravascular volume depletion and other antihypertensive drugs, may affect the safety of concomitant use. Studies have been conducted to determine the effects of tadalafil on the potentiation of the blood-pressure-lowering effects of the alpha-blockers doxazosin and tamsulosin. When tadalafil 20 mg was administered to healthy subjects taking doxazosin (8 mg daily), an alpha-1-blocker, there was significant augmentation of the hypotensive effects of doxazosin. In contrast, coadministration of a single 20-mg dose of tadalafil to healthy subjects taking either 0.4 mg tamsulosin once-daily or 10 mg alfuzosin once daily, both of which are selective alpha-1A-blockers, resulted in no significant decreases in blood pressure. It should be noted that during once daily administration of tadalafil, the presence of continuous plasma tadalafil concentrations may change the potential for interactions with other medications such as alpha-blockers
    Tamsulosin: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
    Tetrabenazine: (Moderate) Tetrabenazine may induce orthostatic hypotension and thus enhance the hypotensive effects of antihypertensive agents. Lower initial doses or slower dose titration of tetrabenazine may be necessary in patients receiving antihypertensive agents concomitantly.
    Tetracaine: (Moderate) Local anesthetics may cause additive hypotension in combination with antihypertensive agents. Use extreme caution with the concomitant use of tetracaine and antihypertensive agents.
    Thalidomide: (Moderate) Thalidomide and other agents that slow cardiac conduction such as alpha-blockers should be used cautiously due to the potential for additive bradycardia.
    Thiopental: (Moderate) Concurrent use of thiopental and alpha-blockers or antihypertensive agents increases the risk of developing hypotension.
    Thiothixene: (Moderate) Thiothixene should be used cautiously in patients receiving antihypertensive agents. Additive hypotensive effects are possible.
    Tizanidine: (Moderate) Concurrent use of tizanidine with antihypertensive agents can result in significant hypotension. Caution is advised when tizanidine is to be used in patients receiving concurrent antihypertensive therapy.
    Trandolapril; Verapamil: (Moderate) The first-dose response (acute postural hypotension) of terazosin can be potentiated by coadministration with beta-blockers. The use of alpha-blockers with verapamil can lead to excessive hypotension; In addition, verapamil has been reported to increase the AUC and Cmax of prazosin and terazosin.
    Tranylcypromine: (Severe) The use of hypotensive agents and tranylcypromine is contraindicated by the manufacturer of tranylcypromine because the effects of hypotensive agents may be markedly potentiated.
    Trazodone: (Minor) Due to additive hypotensive effects, patients receiving antihypertensive agents concurrently with trazodone may have excessive hypotension. Decreased dosage of the antihypertensive agent may be required when given with trazodone.
    Vardenafil: (Major) Concurrent use of phosphodiesterase (PDE5) inhibitors, such as vardenafil, and alpha-blockers may lead to symptomatic hypotension in some patients. An additive effect on blood pressure is anticipated. Patients should be stable on alpha-blocker therapy before starting PDE5 inhibitor therapy. If hemodynamic instability is evident on alpha-blocker therapy alone, there is an increased risk of symptomatic hypotension with concomitant PDE5 inhibitor therapy. For patients who are stable on alpha-blocker therapy, PDE5 inhibitors should be started at the lowest recommended dose. If a patients is currently receiving an optimized dose of a PDE5 inhibitor, alpha-blocker therapy should be initiated at the lowest dose. In general, patients should not be initiated on the orally disintegrating vardenafil tablets while on alpha-blocker therapy; however, if patients have previously used the film-coated tablets, this may be changed to the orally disintegrating tablets upon the advice of the healthcare provider. Stepwise increases in the alpha-blocker dose may be associated with further hypotension when taking a PDE5 inhibitor. Other variables, such as intravascular volume depletion and other antihypertensive drugs, may affect the safety of concomitant use of PDE5 inhibitors and alpha-blockers. Studies have been conducted to determine the effects of vardenafil on the potentiation of the blood-pressure-lowering effects of the alpha-blockers terazosin and tamsulosin. When vardenafil 10 or 20 mg was administered to healthy subjects taking terazosin (10 mg daily), an alpha-1-blocker, there was significant augmentation of the hypotensive effects of terazosin on standing systolic blood pressure. In contrast, coadministration of a single 10 or 20 mg dose of vardenafil to healthy subjects taking 0.4 mg once daily of tamsulosin, a selective antagonist of alpha-1a receptors, resulted in no significant decreases in blood pressure.
    Verapamil: (Moderate) The first-dose response (acute postural hypotension) of terazosin can be potentiated by coadministration with beta-blockers. The use of alpha-blockers with verapamil can lead to excessive hypotension; In addition, verapamil has been reported to increase the AUC and Cmax of prazosin and terazosin.
    Yohimbine: (Moderate) Yohimbine can increase blood pressure and therefore can antagonize the therapeutic action of antihypertensive agents in general. Use with particular caution in hypertensive patients with high or uncontrolled BP.
    Ziprasidone: (Minor) Ziprasidone is a moderate antagonist of alpha-1 receptors and may cause orthostatic hypotension with or without tachycardia, dizziness, or syncope. Additive hypotensive effects are possible if ziprasidone is used concurrently with antihypertensive agents.

    PREGNANCY AND LACTATION

    Pregnancy

    No adequate, well-controlled studies in pregnant women have been done to assess the safety of terazosin during pregnancy. Terazosin should be used during pregnancy only if the benefits to the mother outweigh the risks to the fetus. Terazosin is classified as FDA pregnancy category C.

    Caution is advisable for breast-feeding mothers because it is not known whether terazosin distributes into breast milk. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    MECHANISM OF ACTION

    Mechanism of Action: Terazosin causes peripheral vasodilation by selective, competitive inhibition of vascular postsynaptic alpha1-adrenergic receptors, thereby reducing peripheral vascular resistance and blood pressure. Unlike phenoxybenzamine and phentolamine, which are nonselective alpha-adrenergic blockers, terazosin does not interfere with the feedback mechanism for neurotransmitter release. Because it does not block presynaptic alpha2-receptors, terazosin does not cause reflex activation of norepinephrine release to produce reflex tachycardia. Also, tolerance to its antihypertensive effects does not occur.Terazosin reduces blood pressure in both the supine and standing positions, with more dramatic effects on diastolic blood pressure. These effects are similar to those of prazosin. There is no change in the patient's cardiac output or heart rate, and the response to exercise remains essentially the same.Terazosin also alters lipid metabolism, decreasing the levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) cholesterol. Significant changes were not observed in triglycerides and high-density lipoprotein. The implications of these changes are not known. Terazosin also does not worsen and may improve LVH, does not worsen insulin resistance, and causes only mild sexual dysfunction.In the treatment of benign prostatic hypertrophy, terazosin blocks alpha1-adrenergic receptors present in the smooth muscle of the bladder neck and prostate, allowing the bladder neck and the prostate to relax. This causes less pressure on the urethra and increases urine flow. Terazosin appears to be more effective than finasteride (Proscar) for relieving symptoms associated with BPH.

    PHARMACOKINETICS

    Terazosin is administered orally.  The plasma half-life is about 12 hours. Terazosin is extensively bound to plasma proteins (90—94%) and is metabolized by the liver to one active and three inactive metabolites. Excretion of terazosin occurs as both unchanged drug and metabolites in the urine (40%) and in the feces (60%). Only 10% of the terazosin dose is excreted renally as unchanged drug.

    Oral Route

    Following oral administration, terazosin is almost completely absorbed, with minimal first-pass effect. Food may delay the time to peak concentrations by about 1 hour, but the presence of food has no significant effect on terazosin bioavailability. Antihypertensive effects are seen within 15 minutes, and peak plasma levels are observed approximately 1 hour after administration.